Molecular beam epitaxy of superconducting FeSe${}_x$Te${}_{1-x}$ thin films interfaced with magnetic topological insulators

Abstract

Engineering heterostructures with various types of quantum materials can provide an intriguing playground for studying exotic physics induced by the proximity effect. Here, we report the successful synthesis of iron-based superconductor FeSe${}_x$Te${}_{1-x}$ (FST) thin films across the entire composition range of $0\le x\le 1$ and its heterostructure with a magnetic topological insulator by using molecular beam epitaxy. Superconductivity is observed in the FST films with an optimal superconducting transition temperature $T_c$ $\sim$ 12 K at around x = 0.1. We found that superconductivity survives in the very Te-rich films ($x\le 0.05$), showing stark contrast to bulk crystals with suppression of superconductivity due to an appearance of bicollinear antiferromagnetism accompanied by a monoclinic structural transition. By examining thickness $t$ dependence of magnetic susceptibility and electrical transport properties, we observed a trend where anomalies associated with the first order structural transition broaden in films with below $t\sim$ 100 nm. We infer this observation suggests a suppression of the structural instability near substrates. Furthermore, we fabricated an all chalcogenide-based heterointerface between FST and a magnetic topological insulator (Cr,Bi,Sb)${}_2$Te${}_3$ for the first time, observing both superconductivity and a large anomalous Hall conductivity. The anomalous Hall conductivity increases with decreasing temperature, approaching the quantized value of $e^2/h$ down to the measurable minimum temperature at $T_c$. The result suggests coexistence of magnetic and superconducting gaps at low temperatures opening at the top and bottom surfaces, respectively. Our novel magnetic topological insulator/superconductor heterostructure could be an ideal platform to explore chiral Majorana edge mode.

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Cited by in corpus (11)

• Universal Superconductivity in FeTe and All-Iron-Based Ferromagnetic Superconductor Heterostructures
• Mystery of superconductivity in FeTe films and the role of neighboring layers
• Topological properties of finite-size heterostructures of magnetic topological insulators and superconductors
• Higher-order epitaxy: A pathway to suppressing structural instability and emergent superconductivity
• Control of nonreciprocal charge transport in topological insulator/superconductor heterostructures with Fermi level tuning and superconducting-layer thickness
• Two-dimensional superconducting diode effect in topological insulator/superconductor heterostructure
• Non-Fermi liquid transport and strong mass enhancement near the nematic quantum critical point in FeSe${}_x$Te${}_{1-x}$ thin films
• Studies of superconductivity of Fe chalcogenides in films grown by PLD technique
• Optimizing proximitized magnetic topological insulator nanoribbons for Majorana bound states
• Revealing Superconducting Chiral Edge Modes via Resistance Distributions
• Vacancy Order and Physical Properties of a Ternary Compound Fe0.68Pd0.80Te with an α-Fe1+xTe-Type Structure